There has been known an inkjet printer including a detachable main tank, a sub tank that stores ink supplied from the installed main tank, and an image recording unit that discharges the ink stored in the sub tank and records an image. In the related-art inkjet printer having the above configuration, internal spaces of the main tank and the sub tank are opened to the air. For this reason, when the main tank is installed in the inkjet printer, the ink moves due to a water head pressure so that the liquid level of the main tank and the liquid level of the sub tank are aligned with the same height by the difference between a water head in the internal space of the main tank and a water head in the internal space of the sub tank (hereinafter, referred to as “water head difference”). Then, the inkjet printer displays exchange of the main tank on a display when the residual amount of the ink detected by a residual amount detection sensor is less than a threshold, or displays the fact that the ink is empty. In addition, the inkjet printer prohibits the discharge of ink through the recording unit when the ink becomes empty.